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SERVICE 02
Room-by-room heat loss calculations — remote or on-site.
Independent, professional heat loss calculations for homeowners planning a heat pump, renovating their property or checking their heating requirements — completed remotely using reliable property information, or following an on-site survey where more investigation is needed.
Remote calculations from £195 · On-site surveys from £350
WHY IT MATTERS
Every good heating decision starts with one number per room
A heat loss calculation establishes how much heating a property needs to maintain comfortable indoor temperatures during cold weather. Heat escapes through walls, windows, doors, floors and roofs, and additional heat is lost through ventilation and air infiltration.
A professional calculation considers these losses room by room, rather than estimating a single figure from the property’s floor area. It produces two results: the whole-house heat loss, which helps establish the heat pump capacity required at the local design conditions, and the room-by-room figures, which are used to check whether each radiator or underfloor heating circuit can deliver enough heat.
An Energy Performance Certificate can provide useful background information, but its standardised assumptions are not a substitute for a room-by-room heating design calculation.
Where an external wall’s construction is uncertain, that uncertainty should be resolved as part of the calculation — see when wall U-value testing is worth it.
FIG. 01 — Fabric by fabric, element by element
METHODOLOGY
How a proper calculation is built — and how shortcuts are spotted
If you’ve received quotes with wildly different heat losses, this table is why. Compare what a measured calculation involves against what often passes for one.
COMPARISON — MEASURED CALCULATION VS TYPICAL SHORTCUTS
| Design input | Heat Loss Hub method | Common shortcut | Consequence of the shortcut |
|---|---|---|---|
| Room dimensions | LiDAR-measured on site, every room | Estimated from EPC floor area or satellite photos | ±20–30% error before anything else is considered |
| Wall construction | Verified by inspection — borescope where needed | Assumed from property age band | A filled cavity read as unfilled can double a wall’s calculated loss |
| Ventilation & air changes | Room-by-room rates reflecting real openings and extract fans | Single whole-house default | Old-house losses overstated; kitchens and baths understated |
| Design outside temperature | Your location’s recognised design temperature | Generic UK-wide figure | A Pennine village and a coastal town are not the same design case |
| Room target temperatures | Standard design temperatures, adjusted to how you live | 21 °C everywhere | Bedrooms oversized; open-plan spaces misjudged |
| Output | Watts per room, assumptions stated, auditable | One whole-house kW figure | Impossible to size radiators — or to check anyone’s work |
WHO WE CALCULATE FOR
One service, three kinds of client
HOMEOWNERS
Before the quotes arrive
Walk into every sales conversation already knowing your home’s real heat loss. Installers quote against your numbers — and the ones who argue with measurement tell you something useful about themselves.
Ideal when: you’re early in your journey, or the quotes you have disagree.
TRADE
For heat pump installers
White-label room-by-room calculations and design support for MCS installers who’d rather be installing. Consistent methodology, fast turnaround, documentation that sails through compliance.
Ideal when: your order book is healthy but your design desk isn’t.
PROFESSIONAL
Architects, builders & housing providers
Calculations at plan stage from drawings and specifications, or portfolio-wide surveys for retrofit programmes — independent of any installer’s commercial interest, and consistent across every property.
Ideal when: the numbers need to hold up in front of building control or a budget committee.
YOUR REPORT
What lands in your inbox
- Whole-house heat loss at your local design outside temperature
- Watts per room — every room, individually calculated
- Fabric losses broken down by element: walls, glazing, roof, floor
- Ventilation losses with the air-change assumptions stated
- U-values used, with source or inspection note for each
- Radiator adequacy check at heat-pump flow temperatures (optional)
- Plain-English summary — what the numbers mean for your choices
HONEST BY DESIGN
The number is the product
We have no heat pumps to sell, no installations to win and no reason to nudge your heat loss up or down. If your home loses 5.4 kW, your report says 5.4 kW — even when a bigger number would have made someone’s quote look better.
That’s why installers themselves commission us: an independent calculation is the one document both sides of a contract can trust.
WHY CHOOSE US
We’re independent of equipment sales and installation commissions, with calculations undertaken by a heating-system designer with approximately 18 years of industry experience. We offer flexible surveying — remote assessments where appropriate, with site visits when a property needs more investigation — and a transparent scope that keeps calculation-only work clearly separate from additional design services.
QUESTIONS
Heat loss calculations, explained
Still curious? The Advice Centre covers sizing and why quotes disagree in depth.
Because doing one properly takes hours, and MCS requires it before installation. The problem isn’t paying for engineering — it’s paying several times for several conflicting versions, each owned by a company with a quote to win. One independent calculation, owned by you, ends that cycle.
Not every property needs a physical visit. A remote calculation uses drawings, measurements, photographs and other reliable property information, and isn’t automatically less accurate than one completed on site — what matters is the reliability of the information used. An on-site survey may be more appropriate for older, extended or unusually constructed properties where important details can’t be established remotely. We recommend the method that suits your property rather than automatically charging for a visit.
Good ones welcome it — it saves them unpaid design time and de-risks their installation. Our reports state methodology and inputs so an installer’s own engineer can verify rather than redo them. If an installer insists your measured heat loss is wrong without surveying to the same standard, that’s a red flag worth having found early.
No. An EPC is a broad-brush energy rating built on standardised assumptions; it’s not a design document. Heat pump systems sized from EPC data are a leading cause of the oversizing we see in design reviews.
Remote room-by-room heat loss calculations start from £195, with on-site surveys from £350. The final cost depends on the property: a straightforward home with accurate drawings and reliable measurements may suit a simple remote calculation, while an older property with several extensions or limited documentation may need more investigation. We’ll always confirm the recommended method and the total price before any chargeable work begins.
Typically we need the property address, room dimensions or floor plans, details of windows and doors, and information about the building’s construction and insulation. Don’t worry if you don’t have everything — we’ll explain what’s needed after reviewing your enquiry.
GET THE FACTS FIRST
Know your home's real heat loss before anyone quotes for it
Tell us about your property and we’ll reply by email with the right calculation option for your situation — survey-based or from drawings.
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